Isolated current sensor with codec

ABSTRACT

The present disclosure includes a power measurement, circuit breaker or integrated protection system including isolated analog-to-digital modulators for measuring current using current sensors, such as, for example, current shunts, in a single or multiphase power system. In one embodiment, the modulators are divided into a line-side device with an analog-to-digital modulator and a host-side device including a decimation filter and a processor. In one embodiment, an isolation barrier, such as, for example, a pulse transformer, divides the lineside device from the host-side device.

The present application claims priority to U.S. Provisional ApplicationNo. 61/299,285, filed on Jan. 28, 2010, titled “ISOLATED CURRENTSENSOR,” the entire contents of which is hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to the field of electrical powermeasurement.

BACKGROUND

Electricity is a primary power source used in residential and commercialapplications. Measuring the amount of electricity consumed is animportant task in determining how much to charge a user. In addition,historic trends of electrical consumption are an important tool indetermining how much electricity needs to be produced at any given time.

Electricity is generally delivered over power lines as alternatingcurrent. Electricity can be supplied as single-phase, double-phase, ortriple-phase. Each additional phase generally necessitates using anadditional power line. Additional phases can also be supplied withadditional lines.

Electricity is generally measured in terms of an amount of total powerconsumed. Total power consumption generally involves the integration ofpower used over a specified period of time. Power is the product ofvoltage (V) and current (I). Electricity meters generally measure totalpower consumed by measuring the product of the voltage and the currentat a given instant in time and accumulating (e.g. integrating) theproduct over time.

One way to measure the current is by using a current transformer. Acurrent transformer generally includes a series of coil loops thatencircle a toroidal core. When loaded with a burden resistor, the coilloop produces a voltage proportional to the current running through thepower line. Current transformers are generally preferred for industrialand commercial poly-phase metering due to the current transformer'sinherent DC isolation from phase-to-phase.

A second way to measure current is by using a Rogowski coil. A Rogowskicoil generally includes a toroidal coil placed around a conductor whosecurrent is to be measured. A voltage is induced in the coil which isproportional to the rate of change of the current in the conductor. Theoutput of the Rogowski coil is generally connected to an electricalintegrator circuit in order to provide an output signal that isproportional to the current. Rogowski coils are generally less expensivethan current transformers.

Another way to measure the current is by using a current shunt. Acurrent shunt generally includes a relatively small resistor which isplaced in series with the power line. The current flows through thecurrent shunt creating a small voltage across the shunt. A voltage meterthen measures the voltage drop to determine the amount of currentflowing through the current shunt. Current shunts by themselves are notisolated from the power line and are therefore not preferred formultiphase power measurement as phase-to-phase difference voltagesproduced on the input pins of a power metering device can easily exceedmaximum levels allowed in standard semiconductor products. Currentshunts are generally less expensive than current transformers andRogowski coils, however, due to the isolation issues, currenttransformers are preferred for commercial applications.

SUMMARY

Aspects of the present disclosure include a current sensor and a digitalbarrier for providing electrical isolation. The isolation allows a shuntcurrent sensor to be used in a multiphase power system to determine anaccurate measure of current flow. It also lessens the impact of magneticinterference generally introduced as means of energy theft or tampering.The digital isolation also reduces effects of cross-couplinginterference and improves Electromagnetic Compatibility (EMC) andElectrical Fast Transient (EFT) immunity. The digital barrier isolationalso improves the analog-to-digital conversion's (ADC) effective signalto noise ratio (SNR) by electrically isolating the front end fromhost-side noise sources. The isolation barrier provides phase-to-phaseisolation between power line phases or phases-to-neutral. This allowsthe current sensor to be used to measure multi-phase power or current orsingle-phase power or current with neutral current measurement in a costeffective system. Additionally, in many cases, using digital barrierisolation reduces the overall size of the meter or current protectiondevice (circuit breaker).

In one embodiment, the digital barrier isolation also reduces the amountof intentionally added redundant data need for forward error correction(FEC) by reducing the amount of line-side interference injected into acommunication link between line-side and host-side devices. In otherwords, the digital isolation barrier reduces the extent to whichline-side electromagnetic interference degrades the integrity of thecommunication link by at least partially shielding the communicationlink from electromagnetic interference originating from the line-side.

In one embodiment, the digital barrier isolation also reduces the amountof intentionally added redundant data need for forward error correction(FEC) by reducing the amount of host-side interference injected into acommunication link between line-side and host-side devices. In otherwords, the digital isolation barrier reduces the extent to whichhost-side electromagnetic interference degrades the integrity of thecommunication link by at least partially shielding the communicationlink from electromagnetic interference originating from the host-side.

In one embodiment, a current sensor is used to measure current in apower line. In one embodiment, the current sensor is a current shunt, acurrent transformer, a Rogowski coil, or other device for measuringcurrent. The current sensor is in communication with ananalog-to-digital converter. The analog-to-digital converter is incommunication with a barrier interface module. The barrier interfacemodule is in communication with a barrier isolation module. The barrierisolation module includes, for example, a relatively high-frequencytransformer (such as, for example, a pulse transformer) or a capacitor.The barrier isolation module is in communication with a second barrierinterface module. The second barrier interface module is incommunication with a signal processing circuit. The signal processingcircuit determines an indication of current and power usage and sendsthe indication to a display device or a second processor for furtheranalysis.

In one embodiment, a current sensor is used to measure current in apower line. The current sensor is in communication with ananalog-to-digital converter. The analog-to-digital converter is incommunication with an encoder. The encoder is in communication with abarrier interface module. The barrier interface module is incommunication with a barrier isolation module. The barrier isolationmodule is in communication with a second barrier interface module. Thesecond barrier interface module is in communication with a decodermatched to the encoder. The decoder is in communication with a signalprocessing circuit. In one embodiment, the decoder and signal processingcircuit are included in the same module. The signal processing circuitdetermines an indication of current and power usage and sends theindication to a display device or a second processor for furtheranalysis.

In one embodiment, the encoder function is not related to either the ADCfunction or the isolation function. In one embodiment, the encoderfunction is related to at least one of the ADC function and theisolation function.

In one embodiment, encoding digital values produced by the ADC increasesthe transmitted bit rate so that the transmission across the isolationbarrier is greater than the equivalent of the approximate range of 50Hz-60 Hz, at which the transmission is susceptible to interferencecaused by light. In one embodiment, while the transmitted bit rate ishigher than the bit rate at which the ADC produces digital data values,the data rate of the transmission across the isolation barrier issubstantially equivalent to the bit rate at which the ADC producesdigital data values.

In one embodiment, the encoder includes a method of data encryptionimplemented in a suitable combination of hardware, software andfirmware. In one embodiment, the decoder includes a method ofdeciphering or decrypting data encrypted by the encoder. In oneembodiment, the decoder includes a suitable combination of hardware,software and firmware.

The encoder includes a method of forward error correction implemented ina suitable combination of hardware, software and firmware. In oneembodiment, the decoder includes a method of determining the data mostlikely encoded by the encoder. In one embodiment, the decoder includes asuitable combination of hardware, software and firmware.

In one embodiment, the first circuit or line-side circuit includes apre-amplifier connectable between the current sensor and theanalog-to-digital converter. In operation, the pre-amplifier adjusts themagnitude of the signal provided by the current sensor to theanalog-to-digital converter. In one embodiment, the pre-amplifieramplifies the magnitude of the signal provided by the current sensor. Inone embodiment, the pre-amplifier attenuates the magnitude of the signalprovided by the current sensor. In one embodiment, the pre-amplifierselectively amplifies or attenuates the magnitude of the signal providedby the current sensor.

In one embodiment, a SIGMA-DELTA converter is used to convert adifferential analog signal produced by a current sensor to digital datarepresenting current flowing through the sensor according to Ohm's law.In one embodiment, the SIGMA-DELTA converter is divided into twocircuits which are at least partially electrically isolated from oneanother with a transformer (including, such as, for example, a pulsetransformer) or a capacitor. The transformer provides unidirectionaland/or bidirectional digital data transfer as well as power transferbetween the two parts of the SIGMA-DELTA converter.

In one embodiment, the first circuit, or line-side circuit, includes aSIGMA-DELTA modulator, a voltage reference module, and a barrierinterface module. The line-side circuit manages transmissions of dataand reception of power to and from the isolation barrier. In oneembodiment, the line-side circuit is implemented in a semiconductordevice. In one embodiment, the line-side circuit includes such as, forexample, an entire SIGMA-DELTA converter (e.g. modulator and FIR filter)or other type of analog-to-digital converter. In one embodiment, theSIGMA-DELTA modulator or other analog-to-digital converter is located onthe line-side circuit.

In one embodiment, an encoder is connectable between the SIGMA-DELTAmodulator (or other analog-to-digital converter) and the barrierinterface module. In one embodiment, a decoder is connectable betweenthe second barrier interface module and the FIR filter (or decimationfilter).

In one embodiment, the host-side circuit includes the second half of theSIGMA-DELTA converter which is often referred to as the FIR filter ordecimation filter, and a barrier interface module. The host-side devicemanages transmission of data and power to and from the isolationbarrier. In one embodiment, the host-side device is implemented in asemiconductor device. In one embodiment, the host-side device includesother functions useful in performing functions common in electricitymetering or circuit breaker/protection applications, such as, forexample, voltage sensing, RMS current measurement, power usagecomputation, power usage display, or the like. Although described withrespect to a SIGMA-DELTA converter, a person of skill in the art willunderstand from the disclosure herein that other converters can also beused with the present disclosure.

In one embodiment, the isolation barrier is formed on an integratedcircuit. In one embodiment, the isolation barrier includes ahigh-frequency transformer. In one embodiment, the isolation barrier ison the same chip as either or both of the line-side device and thehost-side device. In one embodiment, the isolation barrier is located ina separate housing from either or both of the line and host-sidedevices.

In one embodiment, power is transmitted from the host-side device to theline-side device through the isolation barrier. In one embodiment,measurement information and/or other communications are sent from theline-side device to the host-side device through the isolation barrier.In one embodiment, command data and/or other communications aretransmitted from the host-side device to the line-side device throughthe isolation barrier.

In one embodiment, there is an optional data path connectable from thehost-side device to the analog-to-digital converter included in theline-side device. The data path allows a host-side processor or othercontroller to change the operation of at least a portion of theanalog-to-digital converter.

In one embodiment, there is a data path from the host-side device to thebarrier interface included in the line-side device. The data path allowsa host-side processor or other controller to change the operation of atleast a portion of the barrier interface.

In one embodiment, the host-side device includes an output data portconnectable to the data path. In one embodiment, the host-side deviceincludes an input data port connectable to the data path. In oneembodiment, the host-side device includes a bidirectional input-outputdata port connectable to the data path.

In one embodiment, the line-side device includes an output data portconnectable to the data path. In one embodiment, the line-side deviceincludes an input data port connectable to the data path. In oneembodiment, the line-side device includes a bidirectional input-outputdata port connectable to the data path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a current measurement device.

FIG. 2 illustrates another embodiment of a current measurement device.

FIG. 3A illustrates an embodiment of a current measurement device with atransformer for use in a one or two phase meter or circuit breaker orintegrated protection device.

FIG. 3B illustrates an embodiment of a current measurement device with atransformer for use in a three phase meter or circuit breaker orintegrated protection device.

FIG. 3C illustrates another embodiment of a current measurement devicewith a transformer for use in a three phase meter.

FIG. 4A illustrates an embodiment of a current measurement device withan external transformer for use in a one or two phase meter.

FIG. 4B illustrates an embodiment of a current measurement device withan external transformer for use in a three phase meter.

FIG. 5 is a flowchart illustrating the current measuring process.

FIG. 6 illustrates an embodiment of a line-side device.

FIG. 7 is a timing chart illustrating line-side and host-sidecommunications.

FIG. 8 illustrates another embodiment of a current measurement device.

FIG. 9 illustrates another embodiment of a current measurement device.

FIG. 10 illustrates another embodiment of a line-side device.

DETAILED DESCRIPTION

FIG. 1 illustrates an embodiment of a current sensor measurement system.A sensor 101, such as, for example, a current shunt, a Rogowski coil, acurrent transformer, or the like, senses the current running through apower line. The sensor 101 is in communication with a line-side device103. The line-side device 103 is in communication with an isolationbarrier 105 which is in communication with a host-side device 107.Although referred to as a line-side device and host-side device, thenames are designations only and are not meant to limit the location ofthe device. In addition, descriptive words, such as, for example,device, module, etc. used herein are meant only to describe certainsections of an overall system and are not meant to limit sections of thesystem to be included in the same, or separate housings or on the sameor separate chips. As one of ordinary skill in the art will understandfrom the present disclosure, various sections of the system can beincorporated into the same or separate housings, boards and/or chips.

The line-side device 103 includes an analog-to-digital converter 109 anda barrier interface 111. The analog-to-digital converter 109, convertsthe analog measurement of current across the current sensor to a digitalvalue. The digital value is then communicated to the barrier interface111 which transmits the digital information across the isolation barrier105 to the host-side device 107.

The isolation barrier 105 includes a high-frequency transformer, such asa pulse transformer which electrically isolates the host-side device 107from the line-side device 103. In one embodiment, a capacitor is used toprovide isolation in addition to the high-frequency transformer orinstead of the high-frequency transformer. The host-side device 107includes a barrier interface 113 and a signal processing circuit 115.The barrier interface 113 transmits power to the line-side device 103and receives data from the line-side device 103. In one embodiment, thebarrier interface 113 transmits data to the line-side device 103, andthe barrier interface 111 receives the data. The barrier interface 113is in communication with the signal processing circuit 115. The signalprocessing circuit 115 determines an indication of power usage andcommunicates the indication for further use, such as, for example, fordisplay by a display device or for communication to a power supplier.

The isolation barrier 105 provides DC and low-frequency isolationbetween the line-side device 103 and the host-side device 107. This isdesirable for multiphase power measurement. In one embodiment, the datarate is relatively low to reduce power consumption and to reduce thesize of the isolation barrier 105. In one embodiment, power is suppliedto the line-side device 103 from the host-side device 107 through theisolation barrier. In one embodiment, the power supplied is less than 50mW. In one embodiment, the power supplied is less than 5 mW. In oneembodiment, data is sent from the line-side device 103 to the host-sidedevice 107 through the isolation barrier 105. In one embodiment, data issent from the host-side device 107 to the line-side device 103 throughthe isolation barrier 105. In one embodiment, data is sentbidirectionally through the isolation barrier 105 to and from the hostand line-side devices 103, 107.

Still referring to FIG. 1, in operation, current flows through the powerline and sensor 101. A voltage representative of the current isgenerated by the sensor 101 and is transmitted to the ADC 109 on theline-side device 103. The ADC 109 can be, such as, for example, aSIGMA-DELTA modulator (SDM). The ADC 109 converts the voltage to adigital value and communicates the digital value to the barrierinterface 111. The barrier interface 111 modulates or otherwisecommunicates the digital value across the isolation barrier 105.Communication across the isolation barrier 105 can be in the form of anintermediate or high-frequency. Using a high-frequency transformer asthe isolation barrier has the added benefit of reducing the size of thetransformer needed. The barrier interface 113 demodulates or receivesthe digital value that was sent across the isolation barrier 105 andcommunicates the digital value to the signal processor 115 forprocessing. The signal processor 115 filters, analyzes, processes,and/or determines a power consumption measurement using the digitalvalue and outputs the measurement. In addition, the barrier interface113 transmits power across the isolation barrier from the host-sidedevice 107 to the line-side device 103 to power the line-side device103. In one embodiment, power is transmitted through the isolationbarrier 105 as a sinusoidal or pulse signal at a frequency that is highrelative to the frequency of the power line. In one embodiment, power istransmitted through the isolation barrier 105 as part of a clock signalwhich is supplied to the analog-to-digital converter. A voltageconverter device (see FIG. 6) included on the line-side device 103transforms a portion of the clock signal to a desired DC voltage by,such as, for example, rectifying and filtering the clock pulse signal.The DC voltage is then supplied to the various components of theline-side device 103. In one embodiment, data is transmitted across theisolation barrier 105 from the line-side device 103 to the host-sidedevice 107 in order to provide, such as, for example, clock information,configuration data, command data, or the like. The clock signal and thedata can be passed back and forth across the isolation barrier 105 atthe same frequency or at different frequencies.

FIG. 2 illustrates an embodiment of a current sensor measurement devicewith a transformer, such as a high-frequency pulse transformer. Currentflowing through a power line is measured using a current sensor 201. Themeasurement device includes a line-side device 203, an isolation barrier205, and a host-side device 207. The line-side device 203 includes ananalog-to-digital converter 209, a barrier interface 211 and a voltagereference 210. The ADC 209 converts an analog input representative ofthe current flowing in the power line into a digital value andcommunicates the digital value to the barrier interface 211. The barrierinterface 213 communicates with the line-side device 207 through theisolation barrier 205. Communication through the isolation barrier 205can be one-way or two-way communication. In one embodiment, the ADCconsists of a SIGMA-DELTA Modulator. In one embodiment, power isreceived by the barrier interface 211 through the isolation barrier 205.A voltage reference 210 communicates received AC power from theisolation barrier 205 and converts the AC power to DC power at a desiredvoltage. The DC power is provided to the line-side device 203, includingthe ADC 209. The barrier interface 211 is in communication with the ADC209 for receiving digitized current information and optionally transmitssampling, clock or other information to the ADC 209.

The host-side device 207 includes a barrier interface 213, a decimationfilter 214, and a signal processing circuit 215. The barrier interface213 allows for communication between the host-side device 207 and theline-side device 203 through the isolation barrier 205, similar to thebarrier interface 211 in the line-side device 203. The barrier interface213 communicates information received from the line-side device to thedecimation filter 214. The decimation filter 214 is a digital filterwhich filters the digital signal received from the line-side device 203.The decimation filter 214 then communicates a filtered digital signalindicative of the voltage across the shunt 201 to the signal processingcircuit 215. The signal processing circuit analyzes the filtered digitalsignal and outputs an indication of current or power running through thepower line.

Still referring to FIG. 2, in operation current flows through the powerline and sensor 201. A voltage proportional to the current is generatedby the sensor 201 and is transmitted to the ADC 209 on the line-sidedevice 203. The ADC 209 converts the voltage to digital values andcommunicates the digital values to the barrier interface 211. Thebarrier interface 211 modulates or otherwise communicates the digitalvalue across the isolation barrier 205. The barrier interface 213demodulates or receives the digital values sent across the isolationbarrier 205 and communicates the digital value to the decimation filter214 for processing. The decimation filter 214 then sends the filtereddigital values to the signal processor for further processing. Thesignal processor 215 filters, analyzes, processes, and/or determines apower consumption measurement using the digital values and outputs themeasurement. In one embodiment, the barrier interface 213 transmitspower across the isolation barrier 205 from the host-side device 207 tothe line-side device 203 to power the line-side device 203. In oneembodiment, power is a relatively high-frequency sinusoidal or pulsepower signal. In one embodiment, power is transmitted through theisolation barrier 111 as part of a clock signal which is supplied to theanalog-to-digital converter. A voltage converter device included on theline-side device transforms a portion of the clock signal to a desiredDC voltage by, such as, for example, rectifying and filtering the clockpulse signal. The DC voltage is then supplied to the various componentsof the line-side device 203. The voltage reference device 210 includedon the line-side device 203 transforms the power signal to a desired DCvoltage. The DC voltage is then supplied to the various components ofthe line-side device 203 for power. In one embodiment, data istransmitted across the isolation barrier 205 from the host-side device207 to the line-side device 203 in order to provide, such as, forexample, clock information, configuration data, command data, or thelike.

FIG. 3A illustrates an embodiment of a current sensor measurement devicewith an internal transformer for use in a single-phase-plus-neutral ortwo-phase meter. FIG. 3A includes two current sensors 301; a line-sidedevice 303, including an ADC 309 and a barrier interface 311; anisolation barrier 305; and a host-side device 307 including a barrierinterface 313, a multiplexer 316, a decimation filter 314, and a signalprocessor 315. The ADC 309, the barrier interfaces 311, 313, theisolation barrier 305, and the decimation filter 314 operate similar tothose described with respect to FIG. 2. In addition to these components,a second current sensor 301 and voltage measurement lines are providedto the host-side device 307. Multiplexer 316 multiplexes the variouscurrent and voltage inputs to the signal processing circuit 315. Thisconfiguration allows for a less expensive measurement device which iscapable of measuring both single and multiphase power by using few chipcomponents. Also optionally included is an attenuation network includingresistors 331 and 332. In an embodiment in which two-phase power ismetered, a third neutral line can also be included with attenuationnetworks from each phase to the neutral line. In one embodiment, the ADCconsists of a SIGMA-DELTA Modulator.

Still referring to FIG. 3A, in operation current flows through the powerlines and sensors 301. A voltage proportional to the current runningthrough each line is generated by the sensors 301 respectively and istransmitted to the ADC 309 on the line-side device 303. The ADC 309converts the voltage to a digital value and communicates the digitalvalue to the barrier interface 311. The barrier interface 311 modulatesor otherwise communicates the digital value across the isolation barrier305. The barrier interface 313 demodulates or receives the digital valuethat was sent across the isolation barrier 305 and communicates thedigital value to the decimation filter 314 for processing. Thedecimation filter 314 then sends the filtered digital value to thesignal processor for further processing. The signal processor 315filters, analyzes, processes, and/or determines a power consumptionmeasurement using the digital value and outputs the measurement. In oneembodiment, the barrier interface 313 transmits power across theisolation barrier 305 from the host-side device 307 to the line-sidedevice 303 to power the line-side device 303. In one embodiment, poweris transmitted in the form of a sinusoidal or pulse power signal or aclock signal. The voltage reference device included on the line-sidedevice 303 transforms the power signal to a desired DC voltage. The DCvoltage is then supplied to the various components of the line-sidedevice 303 for power. In one embodiment, data is transmitted across theisolation barrier 305 from the host-side device 307 to the line-sidedevice 303 in order to provide, such as, for example, clock information,configuration data, command data, or the like.

In addition, the voltage levels of each power line and additionalcurrent values for one or more of the power lines is sent to multiplexer316. Multiplexer 316 multiplexes each of the voltage and additionalcurrent signals and transmits them one or a few at a time to theprocessor 315 for processing.

FIG. 3B illustrates an embodiment which includes three separate isolatedconverters for measuring multiphase power. A person of skill in the artwill understand from the disclosure herein that one, two, three, four,or more isolated converters can be used based on the number of phases ofpower to be measured. In addition, although the neutral line is shownwithout a digital isolation barrier, a person of skill in the art wouldunderstand from the disclosure herein that digital isolation could alsobe used with respect to measuring neutral current. The embodiment ofFIG. 3B includes three isolated converters each including a line-sidedevice 359, an isolation barrier 355, and barrier interfaces 363. In theembodiment of FIG. 3B, a decimation filter 314 is included with thehost-side device 357. Optionally, in one embodiment, a multiplexer canbe used to multiplex the signals from the three barrier interfaces 363through the decimation filter such that only one of the three signals ispassed to the decimation filter at a time. In one embodiment, separatedecimation filters are provided for each converter and all three signalsare passed into the signal processing circuit 365. In addition tomeasuring the current from each phase, voltage from each phase,optionally including the neutral voltage as well as optionally thecurrent through the neutral line are also measured in order toaccurately calculate power consumption. In an embodiment, attenuationnetworks can be optionally included between each phase and the neutralline. FIG. 3B illustrates an embodiment with attenuation networksincluding resistors 385, 386, 387, 388, 389 and 390.

Still referring to FIG. 3B, in operation current flows through the powerlines and sensors 301. A voltage proportional to the current runningthrough each line is generated by the sensors 301 respectively and istransmitted to the line-side devices 359. The ADCs convert the voltageto a digital value and communicate the digital value to the barrierinterface. The barrier interface modulates digital values onto one ormore carrier frequencies or otherwise communicates the digital valueacross the isolation barrier 355. The barrier interface 363 demodulatesor receives the digital value that was sent across the isolation barrier355 and communicates the digital value to the decimation filter 364 forprocessing. The decimation filter 364 then sends the filtered digitalvalue to the signal processor 365 for further processing. The signalprocessor 365 filters, analyzes, processes, and/or determines a powerconsumption measurement using the digital value and outputs themeasurement. In one embodiment, the barrier interface 363 transmitspower across the isolation barrier 355 from the host-side device 357 tothe line-side device 359 to power the line-side device 359. In oneembodiment, power is transmitted in the form of a power signal or clocksignal. A voltage reference device included on the line-side device 359transforms the clock pulses to a desired DC voltage. The DC voltage isthen supplied to the various components of the line-side device 359 forpower. In one embodiment, data is transmitted across the isolationbarrier 355 from the host-side device 359 to the line-side device 357 inorder to provide, such as, for example, clock information, configurationdata, command data, or the like.

In addition, the voltage levels of each power line and additionalcurrent values for one or more of the power lines is sent to multiplexer366. Multiplexer 366 multiplexes each of the voltages and additionalcurrent signals and transmits them one or a few at a time to theprocessor 365 for processing. In one embodiment, multiplexer 366 is ananalog multiplexer and the multiplexed values are converted fromanalog-to-digital values after they are multiplexed. In one embodiment,multiplexer 366 is a digital device and the multiplexed values areconverted from analog-to-digital values before they are multiplexed.

FIG. 3C illustrates an embodiment of a power measurement device with adigital multiplexer. The operation and components are similar to FIG.3B, with the exception that converters 370 are used in order to convertthe analog voltages measured across the power line to a digital value.The digital values are then multiplexed and sent to the signal processor365 for processing. In one embodiment, the current sensors transmitcurrent information to an analog multiplexer which multiplexes thecurrent information for conversion by one or more line-side devicesbefore being transmitted through the isolation barrier. In oneembodiment, the converters are in the host-side device.

FIG. 4A illustrates an embodiment similar to FIG. 3A, with the exceptionthat the isolation barrier 408 is located external to the line andhost-side devices 403, 407. That is, the isolation barrier is notlocated on the same chip with the line-side device 403 and the host-sidedevice 407. Although not illustrated, attenuation networks can also beused with this embodiment as described in FIG. 3A. FIG. 4B illustratesan embodiment similar to FIG. 3B, except that, as discussed above, theisolation barriers 455 are located external to the line-side andhost-side devices 459, 457.

In one embodiment, the line-side device is remote to the host-sidedevice. In one embodiment, the line-side device is housed separatelyfrom the host-side device. In one embodiment, the line-side device islocated on a separate chip and/or board than the host-side device. Inone embodiment, the isolation barrier is located on the same chip and/orboard and/or housing as the line-side device. In one embodiment, theisolation barrier is located on the same chip and/or board and/orhousing as the host-side device. Additionally, other combinations oflocations of the line-side device, host-side device and isolationbarrier are also possible.

FIG. 5 is a flowchart illustrating a process for measuring current. Aspower flows through a power line, an indication of the current is sensedat block 501. The sensed current indication is then converted from ananalog to a digital value at block 503. The digital value is passedthrough an isolation barrier in block 505 as described above. Once thedigital value passes through the isolation barrier, it is processed bythe signal processor and/or decimation filter at block 507. The processthen repeats itself. Parallel current sensing processes, such asdescribed in relation to FIG. 5, can also be used for each additionalphase. Similarly, a single multiplexed process can be used to measurecurrent using an isolation barrier as described above.

FIG. 6 illustrates a block diagram of an embodiment of a line-sidedevice 600. Line-side device 600 includes a pulse transformer 601, apulse IO 603, active rectifiers 605, ADC modulator 607, amplificationblock 608, Temperature (TEMP) circuit 609, fuses 611, bandgap 613,bandgap buffer 615, Ibias 617, Test Multiplexer (TMUX) 619, andInterface block 621.

As described above, the line-side device receives current indicationsfrom a current sensor and transmits digitized current indications to ahost-side device through a digital isolation barrier. Currentindications are received at inputs 623, 625. The indications areamplified at amplification block 608 and are converted to digital valuesby ADC modulator 607. In one embodiment, the gain of amplification block608 is about eight. The converted digital values are communicated to theInterface block 621 for buffering and formatting. The Interface blockcommunicates the digital values to the Pulse IO 603 for transmissionover the digital isolation barrier to the host-side device.

In one embodiment, operating power is received from the host-side devicethrough the isolation barrier 601 in the form of a power pulse asdescribed in further detail with respect to FIG. 7. The power pulse isconverted to operating power (VDD) through the active rectifiers 605. Inone embodiment, the active rectifiers 605 provide a rectifying functionwith less than a drop of about 150 mv when momentary forward current isabout 20 ma. In one embodiment, the host-side device communicatescontrol commands to the line-side device through the isolation barrier601. In one embodiment, the line-side device communicates control,measurement and/or status information through the isolation barrier 601to the host-side device.

Still referring to FIG. 6, the TEMP circuit 609 performs a temperaturemeasurement. In one embodiment, the temperature circuit 609 is used todetermine the reference voltage and bias current communicated to the ADCmodulator through bandgap 613, bandgap buffer 615, and Ibias 617. In oneembodiment, the TEMP circuit 609 waits for an enable signal from theinterface block 621. When it is received, it powers up, completes atemperature measurement and then powers down. In one embodiment, theTEMP circuit 609 only performs a temperature measurement when directedto do so by the host-side device as communicated through the interfaceblock 621. In one embodiment, the TEMP circuit 609 performs a 16 bittemperature measurement. In one embodiment, data from TEMP circuit 609is buffered in the Interface block 621. This is done so that when atemperature output is requested by the host device, the Interface block621 first outputs the buffered value, and then enables the TEMP circuitto create a new value. In one embodiment, the TEMP circuit is a VCOwhose clock frequency is proportional to temperature. In one embodiment,the highest clock rate is 10 MHz. The VCO output is counted for Ppulses. In one embodiment, P is 3800. The final value of the counter isthe TEMP word.

In one embodiment, the fuses 611 provide a programmable memory. In oneembodiment, 8 fuses are provided to store information about theline-side device. The fuses 611 are programmed during manufacture, forexample by blowing one or more of the fuses 611, so as to provideinformation about the line-side device, such as, for example, voltageand current reference information, operating temperatures, manufacturinginformation or other information relevant to the line-side deviceoperation. In one embodiment, the information stored on the fuses areread by the digital block 621 and communicated over the digitalisolation barrier 601 to the host-side device.

In one embodiment, the line-side device 600 includes a 6 pin test modeused to test the line-side device. In one embodiment, the 6 pin testmode is asserted by pulling the INN input 625 to ground. In this mode,VDD and GND are powered directly and the INP input 623 becomes the TMUX619 output. SP and SN continue to be the serial interface. SP and SN canalso be raised above and below the power supplies to evaluate the activerectifier performance. In one embodiment, the current sensor 600includes an 8 pin test mode. This test mode is entered by applying avoltage on a TEST pin input. In this mode, the INN and INP pins 625, 623retain their normal function. In one embodiment, fuse trimming isperformed in either the 6 or 8 pin test mode. In one embodiment, in oneor all test modes, VDD and GND are powered externally to ensuresufficient current for reliable fuse writes. In one embodiment, when afuse read request is received, the contents of the fuse buffer areoutputted. In one embodiment, when the read is completed, the line-sidedevice 600 initiates an internal read sequence to refresh its fusebuffer. After the fuse buffer is refreshed, all fuse circuitry biascurrents are turned off to save supply current.

In one embodiment, the current sensor 600 has a core power supply. Inone embodiment, the current sensor 600 does not have a core powersupply. In one embodiment, the circuitry operates from the VDD supply.In one embodiment, the VDD supply is 3.3 v. In one embodiment, aregulator for the VDD is not included so as to reduce the number ofpins. In one embodiment, a local regulator is used with the bandgap 613,the bandgap buffer 615, and/or the preamplifier gain of the ADCmodulator 607. This would have the effect of maximizing their DC and 60Hz power supply rejection ratio (PSRR). In one embodiment, the turnsratio specification of the transformer is adjusted to keep VDD in areasonable range as the power supply varies. For example, in oneembodiment, the power supply varies from 3.0 v to 3.6 v. In oneembodiment, the turn ratio is 1:1.3. In one embodiment, the powermeasurement device is accurate to about 1% of full scale. In oneembodiment, the power measurement device is accurate to about 0.1% offull scale.

FIG. 7 is a timing diagram of a process of communication between a hostand line-side device over a pulse transformer. Diagram 750 illustratesan embodiment of a process when the test input 710 is low, or, in otherwords, when the line-side device is not in test mode. At power cycle 751N, a write flag (WR) 753 is received by the line-side device. The WRflag 763 initiates the communication of write data. The write dataincludes chop polarity (CHOP POL) instruction 741 and a read codeinstruction (RD CODE) 743. In one embodiment, the WR flag reinitializesthe ADC clock (ADC_CLK) 755, read ADC (RD_ADC) 757 and read data(RD_DATA) 759. In one embodiment, when the test input 711 is high, or,in other words, when the line-side device is in a test mode, the writedata includes additional TMUX and fuse settings 775 information in thewrite data string. In one embodiment, the CHOP POL instruction 741synchronizes polarity inversion of the op-amp. Polarity inversioninverts every other ADC read code 761, 761, 763, 765 of RD_ADC 757 inorder to avoid 60 Hz components in the communication of ADC information.

In one embodiment, output RD_DAT waveforms are immediate and notsynchronized with the pulse clock.

In one embodiment, as illustrated by timing diagram 720, during eachpower cycle, an operating power pulse 701 is received by the line-sidedevice. In addition, during some power cycles, a read pulse or series ofread pulses are transmitted by the line-side device, and/or a writepulse or series of write pulses are received by the line-side device. Inbetween the power pulse and the read and write pulses, are periods ofhigh impedance. The high impedance state allows the pulse transformer tofly back and discharge inductive currents induced by the pulses.

FIG. 8 illustrates another embodiment of a current measurement device,which is similar to the embodiment of the current sensor measurementsystem shown in FIG. 1. A sensor 101 senses the current running througha power line. The sensor 101 is in communication with a line-side device103. The line-side device 103 is in communication with an isolationbarrier 105 which is in communication with a host-side device 107.

The line-side device 103 of FIG. 8 includes a pre-amplifier 108, ananalog-to-digital converter 109, an encoder-decoder module (CODEC) 112and a barrier interface 111.

The pre-amplifier 108 adjusts the magnitude of the signal provided bythe current sensor 101 and provides an output to the analog-to-digitalconverter 109. In one embodiment, the pre-amplifier 108 amplifies themagnitude of the signal provided by the current sensor 101. In oneembodiment, the pre-amplifier 108 attenuates the magnitude of the signalprovided by the current sensor 101. In one embodiment, the pre-amplifier108 selectively amplifies or attenuates the signal provided by thecurrent sensor.

The analog-to-digital converter 109, converts the analog measurement ofcurrent across the current sensor 101 to a digital value. The digitalvalue is then communicated to the CODEC 112.

The CODEC 112 encodes the digital value provided by theanalog-to-digital converter 109. The encoded digital value, or encodeddata, is communicated to the barrier interface 111 which transmits theencoded digital information across the isolation barrier 105 to thehost-side device 107.

In one embodiment the CODEC 112 decodes encoded digital data encoded onand sent from the host-side device 107. In one embodiment the CODEC 112encodes the digital data provided by the analog-to-digital converter 109and also decodes encoded data communicated from the host-side device.Data decoded by the CODEC 112 can be provided to any combination of thecomponents included in the line-side device 103. For example, in oneembodiment decoded data is provided to configure, test or resetcomponents of the analog-to-digital converter 109. Similarly, forexample, in one embodiment decoded data is provided to adjust theoperation of at least one of the pre-amplifier 108 and the barrierinterface 111, or sub-components thereof.

The CODEC 112 is configurable to encode or decode data according tovarious methods of encoding or decoding, in order to implementparticular functions.

In one example, an embodiment of the CODEC 112 includes a method of dataencryption implemented in a suitable combination of hardware, softwareand firmware. Generally, encryption is a method of transforming datainto a form that is unintelligible to other devices that do not have theparticular information (e.g. a key) to enable decryption of theencrypted data. A CODEC including a method of data encryption ordecryption is suitable for systems in which privacy and/or uniqueidentification of particular devices are desirable features. Forexample, in some applications it is desirable to hide informationcollected by a power meters from unverified observers.

Encryption also provides data integrity by reducing the ability ofunauthorized users or devices to manipulate or steal data when it iscommunicated between the line-side device 103 to the host-side device107. In one embodiment, data collected by the line-side device 103 isencrypted before it is communicated to the host-side device 107.

In one embodiment, the CODEC 112 includes a method of deciphering ordecrypting data encrypted on the host-side device 107, implemented in asuitable combination of hardware, software and firmware. As noted above,in one embodiment data from the host-side device 107 is used to adjustthe operation of one or more components of the line-side device 103. Assuch, in hostile environments, including known or unknown hostileinterferers, it is desirable to encrypt data from the host-side device107 to prevent one or more components of line-side device 103 fromerroneous adjustments attempted by known or unknown hostile interferers.

There are various forms and methods of data encryption, as well asvarious forms and methods of deciphering encrypted data. A person ofskill in the art will understand from the disclosure herein that thetype and method of data encryption/decryption is chosen to satisfy therequirements of a particular system. As such, the type and method ofdata encryption/decryption utilized in various embodiments can vary fromone embodiment to the next.

In another example, an embodiment of the CODEC 112 includes a method offorward error correction implemented in a suitable combination ofhardware, software and firmware. Generally, forward error correction isa method of transforming data by adding redundant data prior totransmission. The added redundant data is typically derived as afunction of the data that is encoded. A CODEC including a forward errorcorrection method is useful in systems where information is communicatedover a communication link that causes dynamic phase errors in thetransmitted signal. The added redundant data allows the receiving deviceto detect and correct a bounded number of errors, without requiringretransmission of the original data, as would be required with anAutomatic Repeat request (ARQ)-based protocol.

In one embodiment, the CODEC 112 includes a method of determining thedata most likely encoded by the encoder, implemented in a suitablecombination of hardware, software and firmware. As noted above, in oneembodiment data from the host-side device 107 is used to adjust theoperation of one or more components of the line-side device 103. Also asdescribed above, there are embodiments where the line-side device 103 isremote to the host-side device 107. As such, in one embodiment datatransferred to and from a line-side device 103 to and from a host-sidedevice 107 will travel over a communication link, such as, for example awireless communication link, a satellite communication link, a opticalfiber communication link, etc. Some communication links, such aswireless and satellite communication links, introduce dynamic phaseerrors which corrupt a transmitted signal. Forward error correctionmethods allow a receiver to detect and correct a bounded number oferrors without requiring retransmission of the signal from thetransmitter.

There are various forms and methods of forward error correction, as wellas various forms and methods of decoding received encoded data. A personof skill in the art will understand from the disclosure herein that thetype and method of forward error correction is chosen to satisfy therequirements of a particular system. As such, the type and method offorward error correction utilized in various embodiments can vary fromone embodiment to the next.

In one embodiment, the CODEC 112 encodes the digital values produced bythe analog-to-digital converter 109 such that the transmitted bit rate(which includes the rate at which all data and redundant bits aretransmitted) across the isolation barrier 105 so is greater than theequivalent of the approximate range of 50 Hz-60 Hz, at which thetransmission is sometimes susceptible to interference caused by lightsources. Accordingly, in one embodiment, the transmitted bit rate isgreater than the rate which the analog-to-digital converter 109 producesdigital values that are subsequently encoded by the CODEC 112. In oneembodiment, while the transmitted bit rate across the isolation barrier105 is greater than the rate at which the analog-to-digital converter109 produces digital data values, the data rate of the transmissionacross the isolation barrier 105 is substantially equivalent to the rateat which the analog-to-digital converter 109 produces digital datavalues, so that there is no substantial degradation in the speed withwhich data is transferred from the line-side device 103 to the host-sidedevice 105.

The isolation barrier 105 includes a high-frequency transformer, such asa pulse transformer which electrically isolates the host-side device 107from the line-side device 103. In one embodiment, a capacitor is used toprovide isolation in addition to the high-frequency transformer orinstead of the high-frequency transformer.

The host-side device 107 includes a barrier interface 113, a secondCODEC 116 and a signal processing circuit 115. The barrier interface 113transmits power to the line-side device 103 and receives data from theline-side device 103. In one embodiment, the barrier interface 113transmits data to the line-side device 103, and the barrier interface111 receives the data.

The barrier interface 113 is in communication with the second CODEC 116which is matched to the CODEC 112 on the line-side device 103. Thesecond CODEC 116 is in communication with the signal processing circuit115. The signal processing circuit 115 determines an indication of powerusage and communicates the indication for further use, such as, forexample, for display by a display device or for communication to a powersupplier.

The isolation barrier 105 provides DC and low-frequency isolationbetween the line-side device 103 and the host-side device 107. This isdesirable for multiphase power measurement. In one embodiment, the datarate is relatively low to reduce power consumption and to reduce thesize of the isolation barrier 105. In one embodiment, power is suppliedto the line-side device 103 from the host-side device 107 through theisolation barrier. In one embodiment, data is sent from the line-sidedevice 103 to the host-side device 107 through the isolation barrier105. In one embodiment, data is sent from the host-side device 107 tothe line-side device 103 through the isolation barrier 105. In oneembodiment, data is sent bidirectionally through the isolation barrier105 to and from the host and line-side devices 103, 107. In oneembodiment, data sent from the line-side device 103 is encoded, andsubsequently decoded on the host-side device 107. In one embodiment,data sent from the host-side device 107 is encoded, and subsequentlydecoded on the line-side device 103.

Still referring to FIG. 8, in operation, current flows through the powerline and sensor 101. A voltage representative of the current isgenerated by the sensor 101 and is transmitted to the pre-amplifier 108,which adjusts the magnitude of the signal provided by the current sensor101 and provides an output to the analog-to-digital converter 109. TheADC 109 can be, such as, for example, a SIGMA-DELTA modulator (SDM). TheADC 109 converts the voltage to a digital value and communicates thedigital value to the CODEC 112. The CODEC 112 transforms the digitalvalue into an encoded digital value, and communicates the encodeddigital value to the barrier interface 111. The barrier interface 111modulates or otherwise communicates the encoded digital value across theisolation barrier 105. Communication across the isolation barrier 105can be in the form of an intermediate or high-frequency. Using ahigh-frequency transformer as the isolation barrier has the addedbenefit of reducing the size of the transformer needed. The barrierinterface 113 demodulates or receives the encoded digital value that wassent across the isolation barrier 105 and communicates the encodeddigital value to the second CODEC 116. The second CODEC 116 transformsthe encoded digital value into a decoded digital value. The decodeddigital value is a relatively accurate reproduction of the digital valueprovided by the analog-to-digital converter 109.

The second CODEC 116 communicates the decoded digital value to thesignal processor 115 for processing. The signal processor 115 filters,analyzes, processes, and/or determines a power consumption measurementusing the decoded digital value and outputs the measurement.

In addition, the barrier interface 113 transmits power across theisolation barrier from the host-side device 107 to the line-side device103 to power the line-side device 103. In one embodiment, power istransmitted through the isolation barrier 105 as a sinusoidal or pulsesignal at a frequency that is high relative to the frequency of thepower line. In one embodiment, power is transmitted through theisolation barrier 105 as part of a clock signal which is supplied to theanalog-to-digital converter. A voltage converter device (see FIG. 6)included on the line-side device 103 transforms a portion of the clocksignal to a desired DC voltage by, such as, for example, rectifying andfiltering the clock pulse signal. The DC voltage is then supplied to thevarious components of the line-side device 103. In one embodiment, datais transmitted across the isolation barrier 105 from the line-sidedevice 103 to the host-side device 107 in order to provide, such as, forexample, clock information, configuration data, command data, or thelike. The clock signal and the data can be passed back and forth acrossthe isolation barrier 105 at the same frequency or at differentfrequencies. In one embodiment, at least one of the clock signal and thedata can be encoded on the line-side device 103. In one embodiment, atleast one of the clock signal and the data can be encoded on thehost-side device 107.

FIG. 9 illustrates another embodiment of a current measurement device,which is similar to the embodiment of the current sensor measurementsystem shown in FIG. 2. Current flowing through a power line is measuredusing a current sensor 201. The measurement device includes a line-sidedevice 203, an isolation barrier 205, and a host-side device 207.

The line-side device 203 includes a pre-amplifier 208, ananalog-to-digital converter 209, an encoder-decoder module (CODEC) 212,a barrier interface 211 and a voltage reference 210.

The pre-amplifier 208 adjusts the magnitude of the signal provided bythe current sensor 201 and provides an output to the analog-to-digitalconverter 209. The analog-to-digital converter 109, converts the analogmeasurement of current across the current sensor 201 to a digital value.The digital value is then communicated to the CODEC 212. The CODEC 212encodes the digital value provided by the analog-to-digital converter209. The encoded digital value, or encoded data, is communicated to thebarrier interface 211 which transmits the encoded digital informationacross the isolation barrier 205 to the host-side device 207.

In one embodiment the CODEC 212 decodes encoded digital data encoded onand sent from the host-side device 207. In one embodiment the CODEC 212encodes the digital data provided by the analog-to-digital converter 209and also decodes encoded data communicated from the host-side device207. Data decoded by the CODEC 212 can be provided to any combination ofthe components included in the line-side device 203. For example, in oneembodiment decoded data is provided to configure, test or resetcomponents of the analog-to-digital converter 209 or voltage reference210. Similarly, for example, in one embodiment decoded data is providedto adjust the operation of at least one of the pre-amplifier 208 and thebarrier interface 211, or sub-components thereof The CODEC 212 isconfigurable to encode or decode data according to various methods ofencoding or decoding, in order to implement particular functions.

The barrier interface 211 communicates with the line-side device 207through the isolation barrier 205. Communication through the isolationbarrier 205 can be one-way or two-way communication. In one embodiment,the ADC consists of a SIGMA-DELTA Modulator. In one embodiment, power isreceived by the barrier interface 211 through the isolation barrier 205.A voltage reference 210 communicates received AC power from theisolation barrier 205 and converts the AC power to DC power at a desiredvoltage. The DC power is provided to the line-side device 203, includingthe ADC 209. The barrier interface 211 is in communication with theCODEC 212 for receiving encoded digitized current information andoptionally transmits sampling, clock or other information to the ADC 209via the CODEC 212 or voltage reference 210.

The host-side device 207 includes a barrier interface 213, a secondCODEC 216, a decimation filter 214, and a signal processing circuit 215.The barrier interface 213 allows for communication between the host-sidedevice 207 and the line-side device 203 through the isolation barrier205, similar to the barrier interface 211 in the line-side device 203.The barrier interface 213 communicates encoded information received fromthe line-side device 203 to the second CODEC 216. The second CODEC 216transforms the encoded information into decoded information. In oneembodiment, the decoded information is a relatively accuratereproduction of the information provided by a SIGMA-DELTA modulatorincluded in the analog-to-digital converter 209.

The second CODEC 216 communicates the decoded information to thedecimation filter 214. The decimation filter 214 is a digital filterwhich filters the decoded digital signal received from the line-sidedevice 203. The decimation filter 214 then communicates a filtereddigital signal indicative of the voltage across the shunt 201 to thesignal processing circuit 215. The signal processing circuit analyzesthe filtered digital signal and outputs an indication of current orpower running through the power line.

Still referring to FIG. 9, in operation current flows through the powerline and sensor 201. A voltage proportional to the current is generatedby the sensor 201 and is transmitted to the pre-amplifier 208, whichadjusts the magnitude of the signal provided by the sensor 201. Thepre-amplifier communicates the magnitude adjusted signal to the ADC 209on the line-side device 203. The ADC 209 converts the voltage to digitalvalues and communicates the digital values to the CODEC 212. The CODEC212 transforms the digital values into encoded digital values andcommunicates the encoded digital values to the barrier interface 211.The barrier interface 211 modulates or otherwise communicates theencoded digital value across the isolation barrier 205. The barrierinterface 213 demodulates or receives the encoded digital values sentacross the isolation barrier 205 and communicates the digital value tothe second CODEC 216. The second CODEC 216 transforms the encodeddigital values into decoded digital values and communicates the decodeddigital values to the decimation filter 214 for processing. Thedecimation filter 214 then sends the filtered digital values to thesignal processor for further processing. The signal processor 215filters, analyzes, processes, and/or determines a power consumptionmeasurement using the digital values and outputs the measurement. In oneembodiment, the barrier interface 213 transmits power across theisolation barrier 205 from the host-side device 207 to the line-sidedevice 203 to power the line-side device 203. In one embodiment, poweris a relatively high-frequency sinusoidal or pulse power signal. In oneembodiment, power is transmitted through the isolation barrier 105 aspart of a clock signal which is supplied to the analog-to-digitalconverter. A voltage converter device included on the line-side devicetransforms a portion of the clock signal to a desired DC voltage by,such as, for example, rectifying and filtering the clock pulse signal.The DC voltage is then supplied to the various components of theline-side device 203. The voltage reference device 210 included on theline-side device 203 transforms the power signal to a desired DCvoltage. The DC voltage is then supplied to the various components ofthe line-side device 203 for power. In one embodiment, data istransmitted across the isolation barrier 205 from the host-side device207 to the line-side device 203 in order to provide, such as, forexample, clock information, configuration data, command data, or thelike. In one embodiment, at least one of the clock signal and the datacan be encoded on the line-side device 203. In one embodiment, at leastone of the clock signal and the data can be encoded on the host-sidedevice 207.

FIG. 10 illustrates another embodiment of a line-side device, which issimilar to the embodiment of the line-side device shown in FIG. 6. Theline-side device shown in FIG. 10 includes the elements included in FIG.6, and also includes an encoder-decoder module (CODEC) 612. The CODEC612 is connectable to the analog-to-digital converter 607, and inoperation the CODEC 612 receives digital values from theanalog-to-digital converter 607. The CODEC 612 is also connectable tothe barrier interface block 621, and in operation the CODEC 612communicates encoded digital values to the barrier interface block 621.

As described above, with reference to FIG. 8, in one embodiment theCODEC 612 decodes encoded digital data encoded on and sent from thehost-side device. In one embodiment the CODEC 612 encodes the digitaldata provided by the analog-to-digital converter 607 and also decodesencoded data communicated from the host-side device. Data decoded by theCODEC 612 can be provided to any combination of the components includedin the line-side device. For example, in one embodiment decoded data isprovided to configure, test or reset components of the analog-to-digitalconverter 607. Similarly, for example, in one embodiment decoded data isprovided to adjust the operation of at least one of the pre-amplifier608 and the barrier interface block 621, or sub-components thereof.

The CODEC 612 is configurable to encode or decode data according tovarious methods of encoding or decoding, in order to implementparticular functions.

In one example, an embodiment of the CODEC 612 includes a method of dataencryption implemented in a suitable combination of hardware, softwareand firmware. Generally, encryption is a method of transforming datainto a form that is unintelligible to other devices that do not have theparticular information (e.g. a key) to enable decryption of theencrypted data. A CODEC including a method of data encryption ordecryption is suitable for systems in which privacy and/or uniqueidentification of particular devices are desirable features. Forexample, in some applications it is desirable to hide informationcollected by a power meters from unverified observers.

Encryption also provides data integrity by reducing the ability ofunauthorized users or devices to manipulate or steal data when it iscommunicated between a line-side device to and a host-side device. Inone embodiment, data collected by the line-side device is encryptedbefore it is communicated to the host-side device.

In one embodiment, the CODEC 612 includes a method of deciphering ordecrypting data encrypted on the host-side device, implemented in asuitable combination of hardware, software and firmware. As noted above,in one embodiment data from the host-side device is used to adjust theoperation of one or more components of the line-side device 103. Assuch, in hostile environments, including known or unknown hostileinterferers, it is desirable to encrypt data from the host-side deviceto prevent one or more components of line-side device 103 from erroneousadjustments attempted by known or unknown hostile interferers.

There are various forms and methods of data encryption, as well asvarious forms and methods of deciphering encrypted data. A person ofskill in the art will understand from the disclosure herein that thetype and method of data encryption/decryption is chosen to satisfy therequirements of a particular system. As such, the type and method ofdata encryption/decryption utilized in various embodiments can vary fromone embodiment to the next.

In another example, an embodiment of the CODEC 612 includes a method offorward error correction implemented in a suitable combination ofhardware, software and firmware. Generally, forward error correction isa method of transforming data by adding redundant data prior totransmission. The added redundant data is typically derived as afunction of the data that is encoded. A CODEC including a forward errorcorrection method is useful in systems where information is communicatedover a communication link that causes dynamic phase errors in thetransmitted signal. The added redundant data allows the receiving deviceto detect and correct a bounded number of errors, without requiringretransmission of the original data, as would be required with anAutomatic Repeat reQuest (ARQ)-based protocol.

In one embodiment, the CODEC 612 includes a method of determining thedata most likely encoded by the encoder, implemented in a suitablecombination of hardware, software and firmware. As noted above, in oneembodiment data from the host-side device is used to adjust theoperation of one or more components of the line-side device. Also asdescribed above, there are embodiments where the line-side device isremote to the host-side device. As such, in one embodiment datatransferred to and from a line-side device to and from a host-sidedevice will travel over a communication link, such as, for example awireless communication link, a satellite communication link, a opticalfiber communication link, etc. Some communication links, such aswireless and satellite communication links, introduce dynamic phaseerrors which corrupt a transmitted signal. Forward error correctionmethods allow a receiver to detect and correct a bounded number oferrors without requiring retransmission of the signal from thetransmitter.

There are various forms and methods of forward error correction, as wellas various forms and methods of decoding received encoded data. A personof skill in the art will understand from the disclosure herein that thetype and method of forward error correction is chosen to satisfy therequirements of a particular system. As such, the type and method offorward error correction utilized in various embodiments can vary fromone embodiment to the next.

Although the foregoing invention has been described in terms of certainpreferred embodiments, other embodiments will be apparent to those ofordinary skill in the art from the disclosure herein. For example, askilled artisan will recognize from the disclosure herein that variousmethods of manufacture, design, and materials can be used to make thevarious components described herein. For example, instead of using acurrent shunt, a person of ordinary skill in the art would understandthat other devices for measuring current could also be used, such as,for example, a current transformer, Rogowski coil or the like.Additionally, other combinations, omissions, substitutions andmodifications will be apparent to the skilled artisan in view of thedisclosure herein. It is contemplated that various aspects and featuresof the invention described can be practiced separately, combinedtogether, or substituted for one another, and that a variety ofcombination and sub-combinations of the features and aspects can be madeand still fall within the scope of the invention. Furthermore, thesystems described above need not include all of the modules andfunctions described in the preferred embodiments. Accordingly, thepresent invention is not intended to be limited by the recitation of thepreferred embodiments, but is to be defined by reference to the appendedclaims.

1. A current measurement system comprising: a line-side device thatincludes: a current sensing device, the current sensing deviceconfigured to generate a voltage proportional to current flowing from apower source; an analog-to-digital converter in communication with thecurrent sensing device, the analog-to-digital converter configured toconvert the voltage to first digital data; and an encoder incommunication with the analog-to-digital converter, the encoderconfigured to transform the first digital data into encoded digitaldata; a host-side device that includes: a decoder configured totransform the encoded digital data into decoded digital data; and aprocessor in communication with the decoder configured to compute anindication of a power consumption based in part on the decoded digitaldata; and an isolation barrier configured to provide at least partialelectrical isolation between the encoder and the decoder, whereinoperating power is supplied from the host-side device to theanalog-to-digital converter through the isolation barrier, whereinsecond digital data is provided from the host-side device to theline-side device through the isolation barrier, and wherein the encodeddigital data is provided to the decoder through the isolation barrier.2. The current measurement system of claim 1, further comprising firstand second barrier interface devices for communication through theisolation barrier, wherein the first barrier interface device isconfigured to transmit information across the isolation barrier, and thesecond barrier interface device is configured to receive informationfrom across the isolation barrier.
 3. The current measurement system ofclaim 2, wherein the processor computes the power consumption using theinformation transmitted across the isolation barrier.
 4. The currentmeasurement system of claim 2, wherein the encoder is in communicationwith the first barrier interface device and the second barrier interfacedevice is in communication with the decoder.
 5. The current measurementsystem of claim 1, wherein the analog-to-digital converter comprises amodulator portion of a SIGMA-DELTA converter.
 6. The current measurementsystem of claim 5, wherein the SIGMA-DELTA converter comprises an analogSIGMA-DELTA modulator.
 7. The current measurement system of claim 5,further comprising a digital filter configured to filter the decodeddigital data before the decoded digital data is received by theprocessor.
 8. The current measurement system of claim 7, wherein thefilter comprises a decimation filter.
 9. The current measurement systemof claim 1, further comprising two or more analog-to-digital converters,two or more encoders, two or more encoders and two or more isolationbarriers configured to measure two or more phases of power across two ormore current sensing devices.
 10. The current measurement system ofclaim 1, wherein the isolation barrier comprises a pulse transformer.11. The current measurement system of claim 1, wherein a clock signal isprovided to the analog-to-digital modulator through the isolationbarrier.
 12. The current measurement system of claim 1, whereinoperational power is transmitted across the isolation barrier.
 13. Thecurrent measurement system of claim 1, wherein the encoder is configuredto encode the first digital data using forward error correction.
 14. Thecurrent measurement system of claim 13, wherein the encoder isconfigured to encode the first digital data such that a transmitted datarate across the isolation barrier is substantially equivalent to therate at which the analog-to-digital converter produces digital valuesfor encoding by the encoder.
 15. The current measurement system of claim1, wherein the encoder is configured to encode the first digital datausing encryption.
 16. A current measurement system comprising: a currentsensing device, the current sensing device configured to generate avoltage proportional with a current flowing from a power source; ananalog-to-digital converter in communication with the current sensingdevice, the analog-to-digital converter configured to convert thevoltage to digital data; a first encoder in communication with theanalog-to-digital converter, said the first encoder configured totransform the digital data into encoded digital data; a first decoderconfigured to transform the encoded digital data into decoded digitaldata; a processor in communication with the first decoder configured tocompute an indication of a power consumption based in part on thedecoded digital data; and an isolation barrier configured to provide atleast partial electrical isolation between the first encoder and thefirst decoder, wherein operating power and a digital signal are suppliedto the analog-to-digital converter through the isolation barrier in afirst direction and wherein the encoded digital data is provided to thefirst decoder through the isolation barrier in a second direction. 17.The current measurement system of claim 16, further comprising: a datasource configured to provide the digital signal; a second encoder incommunication with the data source, the second encoder configured totransform the digital data into an encoded digital signal; a seconddecoder configured to transform the encoded digital signal into adecoded digital signal; and wherein the isolation barrier configured toprovide at least partial electrical isolation between the second encoderand the second decoder.
 18. The current measurement system of claim 17,wherein the data source is included within the processor.
 19. Thecurrent measurement system of claim 17, wherein the digital signalincludes a control signal.
 20. The current measurement system of claim17, wherein the decoded digital signal is utilized for power.
 21. Adevice comprising: an analog-to-digital converter configured to convertan indication of a current flowing through a power source from an analogto digital values; an encoder in communication with theanalog-to-digital converter, the encoder configured to transform thedigital values into encoded digital values; a decoder configured totransform the encoded digital values into decoded digital values; adecimation filter configured to decimate the decoded digital values togenerate decimated values; a processor configured to receive thedecimated values and the indication of the current, compute a powerusage measurement, and generate a digital signal; and an isolationbarrier configured to provide electrical isolation between signals sentfrom the encoder to the decoder, provide the decimated values to theprocessor in a first direction, and provide the digital signal from theprocessor to the analog-to-digital converter in a second direction. 22.The device of claim 21, wherein the isolation barrier comprises a pulsetransformer.
 23. The device of claim 21, further comprising a currentshunt configured to provide the indication of the current flowingthrough the power source to the analog-to-digital modulator.
 24. Thedevice of claim 21, wherein the analog-to-digital converter and thedecimation filter comprise a SIGMA-DELTA device.
 25. The device of claim21, wherein the isolation barrier comprises a pulse transformer.
 26. Thedevice of claim 21, wherein operational power is transmitted across theisolation barrier.
 27. The device of claim 21, further comprising firstand second barrier interface devices for communication through theisolation barrier, wherein the first barrier interface device isconfigured to transmit information across the isolation barrier, and thesecond barrier interface device is configured to receive informationfrom across the isolation barrier.
 28. The device of claim 27, whereinthe encoder is in communication with the first barrier interface deviceand the second barrier interface device is in communication with thedecoder.
 29. The device of claim 27, wherein the encoder is configuredto encode the digital values using forward error correction.
 30. Thedevice of claim 29, wherein the encoder is configured to encode thedigital values such that a transmitted data rate across the isolationbarrier is substantially equivalent to a rate at which theanalog-to-digital converter produces digital values for encoding by theencoder.
 31. The device of claim 27, wherein the encoder is configuredto encode the digital values using encryption.
 32. A method of measuringpower comprising: converting an indication of current flowing through apower source from an analog current signal to a digital current signalon a line-side portion of a power measurement device; encoding thedigital current signal into an encoded digital current signal on theline-side portion; communicating the encoded digital current signal fromthe line-side portion through an electrical isolation barrier to ahost-side portion of the power measurement device; communicating adigital information signal from the host-side portion to the line-sideportion through the electrical isolation barrier; decoding the encodeddigital signal into a decoded digital current signal on the host-sideportion; decimating the decoded digital current signal; determining anindication of a voltage across a power source; and calculating a powerconsumption measurement.
 33. The method of claim 32, wherein convertingcomprises over-sampling.
 34. The method of claim 32, whereincommunicating comprises inverting every other bit.
 35. The method ofclaim 32, further comprising transmitting operating power over theisolation barrier from the host-side to the line-side.
 36. A devicecomprising: one or more analog-to-digital converters configured toconvert indications of current flowing through a multi-phase powersource from an analog to digital values; one or more encoders configuredto transform the digital values into encoded digital values; one or moreencoders configured to transform the encoded digital values into decodeddigital values; one or more decimation filters configured to decimatethe decoded digital values to generate decimated values; a processorconfigured to receive the decimated values and the indications ofcurrent and compute a power usage measurement, and to generate a digitalinformation signal; and one or more isolation barriers configured toprovide electrical isolation between signals sent from the encoder tothe decoder, wherein the isolation barriers communicate the decimatedvalues in a first direction, and communicate the digital informationsignal in a second direction.
 37. The device of claim 36, wherein theone or more isolation barriers comprise a pulse transformer.
 38. Thedevice of claim 36, further comprising one or more current shuntsconfigured to provide the indication of current flowing through thepower source to the analog-to-digital modulator.
 39. The device of claim36, wherein the one or more analog-to-digital converters and the one ormore decimation filters comprise a SIGMA-DELTA device.
 40. The device ofclaim 36, wherein the one or more isolation barriers comprise a pulsetransformer.
 41. The device of claim 36, wherein operational power istransmitted across one or more the isolation barriers.
 42. The device ofclaim 36, further comprising first and second barrier interface devicesfor communication through the isolation barrier, wherein the firstbarrier interface device is configured to transmit information acrossthe isolation barrier, and the second barrier interface device isconfigured to receive information from across the isolation barrier. 43.The device of claim 42, wherein the encoder is in communication with thefirst barrier interface device and the second barrier interface deviceis in communication with the decoder.
 44. The device of claim 36,wherein the encoder is configured to encode the digital values usingforward error correction.
 45. The device of claim 44, wherein theencoder is configured to encode the digital values such that atransmitted data rate across the isolation barrier is substantiallyequivalent to a rate at which the analog-to-digital converter producesdigital values for encoding by the encoder.
 46. The device of claim 36,wherein the encoder is configured to encode the digital value usingencryption.
 47. A method of measuring power consumed in a multi-phasesystem comprising: converting two or more indications of current flowingthrough a multi-phase power source from analog current signals to adigital current signals on one or more line-side portions of a powermeasurement device; encoding the digital current signals into encodeddigital current signals on the one or more line-side portions;communicating the encoded digital signals from the one or more line-sideportions through one or more electrical isolation barriers to one ormore host-side portions of the power measurement device; communicating adigital information signal from the one or more host-side portions tothe one or more line-side portions through the electrical isolationbarrier; decoding the encoded digital current signals into decodeddigital current signals on the one or more host-side portions;decimating the decoded digital current signals; determining indicationsof voltages across the multi-phase power source; and calculating a powerconsumption measurement.
 48. The method of claim 47, wherein convertingcomprises over-sampling.
 49. The method of claim 47, wherein encodingcomprises inverting every other bit.
 50. The method of claim 47, furthercomprising transmitting operating power over the one or more isolationbarriers from the host-side to the line-side.